For holographic projections, one desires to increase the size of the spatial envelope and the quantity of eyeboxes arrayed within the envelope, whereby the viewer has a bigger zone in which to experience parallax. One important advance in this area is shown by U.S. Pat. No. 4,799,739 to Newswanger. There, a holographic optical element is used as a projection screen for a multiplicity of projectors. The projectors are placed so eyeboxes where their images are seen become horizontally contiguous, thereby achieving a parallax effect. My viewing system improves upon Newswanger's concept. My system is less bulky and complex in that only one projector is used, and my system lets viewers see a perspective change over a greater range of head movement than does Newswanger. Further, my system adjusts both for relatively small and relatively large head movements of the human viewer.
In my method, sequences of images are sent very rapidly from a projector, the images being views of a scene or object from different angles of perspective. The images may go directly to an arcuate mirror from a projector which pivots to aim at varied locations on the arcuate mirror. But preferably, the projector is stationary and the images are sent from it to a spinning polygonal mirror, which reflects the images to the arcuate mirror. A flat mirror, which pivots in response to viewer head motion, receives the images from the arcuate mirror and reflects them back to an appropriate zone of the arcuate mirror.
The arcuate mirror has a multiplicity of these zones. Each zone is dedicated to a particular range of viewer head positions and to a particular sequence of images; each image reflects from a different, characteristic location within its dedicated zone. Once images reflect from the appropriate zone of the arcuate mirror, they pass through a holographic optical element (HOE) to create an eyebox array. In my system, any given sequence of images creates an array of eyeboxes whose width accommodates relatively small sideways head motions of the viewer. Since the eyeboxes are densely packed, they create fine parallax for the viewer. Adapting to larger head motions is done by coordinating the sequence of images with the flat mirror's position.